Low temperature liquified gas storage tank

ABSTRACT

A low temperature liquified gas storage tank having a rigid outer wall and a low temperature resistant, liquid tight inner wall formed of barrier members made of plywood, sheet metal or plastic. Joists fixed to the outer wall extend along the joints between the side edges of adjacent barrier members, are secured thereto, and the inner surface of each barrier member within the area bounded by the joists is supported by the outer surface of a pressure pad carried by the outer wall so as to permit relative thermal expanding and contracting movements between each pressure pad and the barrier member supported thereby.

United States Patent Noma et al. 1 Jan. 28, 1975 [54] LOW TEMPERATURELIQUIFIED GAS 3.339.778 9/1967 Herrenschmidt 330/15 STORAGE TANK 12331331311335 ilklfil '41 ll}? [75] In ento s: Tetsuo Noma; Osamu agao: c u3:694986 /1972 Yamamoto et al. 220/ Okano, all of Osaka. Japan FORElGNPATENTS OR APPLICATIONS [73] Assgneei i Smpbmldmg and 2014.174 10/]966Sweden 220/9 1.0 jEngmeermg Cmnpanh 8%.267 6/l962 Great Britain 220/9 LGapan [22] Filed: July 7, 1972 Primary Examiner-William l. PriceAssistant ExaminerStephen Marcus PP 269,568 Attorney, Age/11,7Firm-Farley, Forster and Farley Foreign Application Priority Data [571'ABSTRACT Sept. 11, 1971 Japan 46-70699 A low temperature quified Swmgctank having a rigid outer wall and a low temperature resistant, liquid2% 2 x 73 j, g tight inner wall formed of barrier members made of i 56 F9 LG 217/65. P ywood, sheet metal or plastic. .loists fixed to the l 1 0care 52 6 6 outer wall extend along the joints between the side I edgesof adjacent barrier members, are secured 56 R f Ct d thereto, and theinner surface of each barrier member L 1 evergnces within the areabounded by the joists is supported by UNITED STATES PATENTS the outersurface of a pressure padcarried by the 67.035 7/1867 Foley 220/15 outerwall so as to' permit relative thermal expanding 2263,9 3 11/ 41 ar e-m. .220/l5 and contracting movements between each pressure 5 iigzi g tiiiiiii pad and the barrier member supported thereby. os'er..... 3,1l2,043 ll/l963 Tucker 220/15 8 Claims, 9 Drawing Figures PATENTED JAN 28 I975 SHEET 10F 1' FIG.|

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PATENTEUJANZBIBIS I LOW TEMPERATURE LIQUIFIED GAS STORAGE TANK SUMMARYOF THE INVENTION The present invention relates to an improvedconstruction for a low temperature liquified gas storage tank and morespecifically to a low temperature liquified gas storage tank of aconstruction in which a tank inner wall, made of low temperatureresistant and liquid tight barrier members, is supported by means ofjoists in inwardly spaced relation to a rigid outer wall of the tank.

Safety and saving of expenses in particular should be pursued for alarge sized tank for storing a low temperature liquified gas, because itis necessary to ensure that the gas does not leak and that the tank doesnot collapse under the extremely low temperature, such as minus I62C, towhich atank of this kind is subjected. It is less desirable as a matterof course, however, to use a great deal of expensive metal which iscapable of withstanding such extremely low temperatures.

To attain these objectives, it is advisable to construct the tank innerwall out of barrier members, made of liquid tight plywood or sheet metalwhich is resistant to low temperature, inside of and insulated from arigid tank outer wall which is made of normal steel plate, with a woodenframework supporting the inner wall on the outer one. Naturally in thiscase, study is invited to the tank inner wall with regard to the liquidpressure applied thereto and to the expansion and contraction thereofcaused by the charging and discharging of the low temperature liquid.For example, when using liquid tight plywood panels for the tank innerwall, the plywood is required to have enough thickness to withstand theliquid pressure even though it is supported by means of joists. Asthermal stress created on the plywood increases proportionally to theincrement of its thickness, a very great stress is introduced at thejoints thereof between adjacent panels. In a structure in which theplywood panels are fixed to the tank outer wall, a joint between panelsin the same plane is balanced in stress since both sides thereof areequally stressed in opposite directions, but a joint in a corner of thetank must be of substantial construction, because it is stressed only onone side thereof. Therefore, a problem arises in that the thick plywood-is difficult to mount fixedly on the tank wall.

As is apparent from the foregoing, the tank inner wall needs the tworequisites of a liquid tight nature and pressure resistivity. In orderto solve this problem, this invention furnishes the inner wall with theliquid-tight nature through the use of barrier members and separatelyprovides the pressure resistivity through a pressure resistingconstruction of the wall, in order to reduce the thickness of thebarrier members, thus preventing great stress from arising on thebarrier members clue to the temperature variation that is caused by thecharging and discharging of the low temperature liquified gas.Therefore, the barrier members can be fixed firmly without wrinkling thebarrier members or making the joints between them expandable, andmoreover, the barrier members can bear the liquid pressure adequately.

The present invention employs pressure supporting pads fixed on the tankouter wall to support the barrier members from their back side overnearly their entire surface area, and the pads are permitted tounrestrictedly expand or contract relative to the barrier members sothat the pads do not transmit their thermal expansion or contractionthereto. For the low temperature resistant and liquid tight barriermembers, plain, liquid tight, and standard size plywood or sheet metalor synthetic resin plate is employed which is of low thermal stress, andthe barrier member joints are fitted firmly on coupling joists fixed onthe tank outer wall.

With such structure, the tank can be very simple in construction and asharp reduction in cost can be achieved in comparison with conventionalstructures in which the barrier members with a great thermal stress arewrinkled or corrugated to promote the expansion or contraction thereof,and a so-called expandable construction is used for the joints thereofinstead of fixing the joints firmly on the coupling joists. Moreover, inthe present invention, a barrier member does not need to be thick enoughto carry the liquid pressure in itself, since its surface is supportedby means of the supporting pads, and for this reason, a thinner barriermember is employed for the tank inner wall to reduce the thermal stress.Thermal expansion or contraction cannot affect the fixing of the barriermember joints on the joists, because the expansion or contraction of thepressure supporting pads is not transmitted to the barrier members.

Other features and advantages of the present invention will be apparentfrom the following description of the preferred embodiments illustratedin the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view ofa lowtemperature liquified gas storage tank;

FIG. 2 is a fragmentary enlarged sectional view of a tank constructed inaccordance with the-present invention;

FIG. 3 is an enlarged sectional view showing the construction of a jointbetween plywood barrier members;

FIG. 4 is an enlarged sectional view showing the construction of a jointbetween sheet metal barrier members;

FIG. 5 is a sectional view similar to FIG. 4, but showing an alternateconstruction of a joint between sheet metal barrier members;

FIG. 6 is an enlarged sectional view showing the construction of a jointbetween barrier members formed of synthetic resin plates;

FIG. 7 is a plan view of a portion of the inner wall of the tank showinga standard sized barrier member;

FIG. 8 is an enlarged sectional view showing a spot attachment of asheet metal barrier member to a pressure pad; and,

FIG. 9 is a sectional view similar to FIG. 8, but showing an alternateconstruction for a barrier member of synthetic resin plate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, numeral 1 is a tankouter wall made of normal steel plate and is equivalent to a tankoutside shell located in the earth or to a wall of the inner hull in atransporting vehicle such as a ship. Numeral 2 is a low temperatureresistant and liquid tight tank inner wall, located at a necessary spacefor heat insulation inwardly from the tank outer wall 1. Heat insulatingmaterial 3 is inserted between this inner wall 2 and the outer wall 1.

The inner wall 2 is made of low temperature resistant and liquid tightbarrier members 8 joined together, these barrier members all beingplanar, or a standard size, and low in thermal stress. This kind ofbarrier member may be plywood 5, as shown in FIG. 3, having an innerlayer ofliquid tight material 4 such as resin impregnated paper or a lowtemperature resistant metal film; or may be, as illustrated in FIGS. 4and 5, a material which is low in Youngs modulus and has a relativelywide elastic range such as aluminum or copper, or alternately a lowtemperature resistant metal sheet 6 having a low coefficient of thermalexpansion, such as 36 percent nickel steel; or, may be a low temperatureresistant synthetic resin plate 7, as illustrated in FIG. 6.

The joints 9 between the barrier members 8 are fixed firmly on couplingjoists 10, as shown in FIG. 3 to FIG. 6, which will be described indetail later on. The coupling joists 10 are arranged in checkerboardfashion, are composed of plywood, and include legs 12 which are firmlyattached to the joists 10 in places through angle pieces 11 to form asectionally T-shaped configuration. The legs 12 are fixed to the tankouter wall 1 through angle pieces 13, as illustrated in FIG. 2.

Numeral 14 designates pressure pads each provided with a planar liquidpressure supporting surface 15 to support a barrier member 8 behind mostof the surface area thereof. These pads are each made of a pad plate 16formed of plywood and of leg plates 18 attached firmly adjacent to theperimeter of the pad plate through angle pieces 17. A pad 14 is placedbetween each barrier member 8 and the tank outer wall 1, and the legplates 18 are fixed on the tank outer wall 1 through angle pieces 19.The above-mentioned liquid pressure supporting surface 15 supports eachbarrier member 8 so as to permit relative thermal expansion andcontraction between the pressure pad 14 and the barrier member 8supported thereby.

The manner in which the barrier member joints 9 are fixed on thecoupling joists 10 is described as follows:

Referring to FIG. 3, showing plywood panels 5 used .for the barriermembers 8, the plywood above the layer of liquid tight material 4 is cutaway from adjacent edges 20 of each panel to a certain width to bare theliquid tight material. A strip of patching material 21 is attached tothe bared portions 4a of the liquid tight material at the left and righthand sides of the adjacent edges of the panels by means of a lowtemperature resistant adhesive 22, and both plywood panels 5 are securedto the coupling joist 10 by driving nails or wood screws 23 through thestrip of patching material 21 into the coupling joist 10 through both ofthe plywood panels 5. Moreover, the strip of patching material 21 andbared portions 4a liquid tight material are covered with a lowtemperature adhesive 24, thus completely preventing liquid from leakingthrough the joint 9.

FIG. 4 illustrates a coupling joist 10 and the joint 9 between lowtemperature resistant metal sheets 6 used for the barrier members 8, theadjacent edges of the sheets being connected by means of welding 25.Numeral 26 is a backing strip laid under the joint 9 of the sheets 6,and 27 is a refractory material such as asbestos to prevent welding heatfrom scorching the coupling joist 10. The sheets 6 welded at the joint 9thereof are secured to the coupling joist 10 through the backing stripwith wood screws 28 at both sides of the welded joint. In order toprevent liquid from leaking, these screws are sealed to the sheets 6around their circumference by means of welding or adhesive 29.

In FIG. 5, the low temperature resistant metal sheets 6 are attached bymeans of adhesive 32 to a backing strip 31 fitted on the coupling joist10 by means of adhesive 30, and are further secured to the couplingjoist 10 by means of wood screws 33. The heads of these screws arecovered with low temperature resistant adhesive 34 and in this case, theadhesive is also inserted between adjacent edges of both sheets.Consequently, a joint construction is achieved which prevents liquidfrom leaking.

FIG. 6 shows synthetic resin plates 7 employed for the barrier members8. Numeral 35 identifies a'synthetic resin patching material attachedonto the coupling joist 10 with adhesive 36. The synthetic resin plates7 are fixed at the joint 9 thereof onto the above mentioned patchingmaterial 35 by means of adhesive 37 and are further fitted by means ofadhesive 39 with a synthetic resin coating material 38 so as to coverthis joint 9.

As will be understood from the foregoing description of FIGS. 3 to 6,the barrier member joint 9 can be fixed onto the coupling joist 10 bymeans suitable for the properties and nature of the barrier member 8.

Since each barrier member 8 only rests on the supporting surface 15 ofone of the pressure pads 14 so as to permit relative thermal expandingor contracting movements, and particularly when the low temperatureresistant metal sheet 6 is employed for the barrier members 8, thesheets 6 at the side or top walls of the tank are apt to be distorted byswelling or saggingas a result of the sheet metal being very thin. Inthis case, as illustrated in FIGS. 7 and 8, the barrier member 8 can besecured to the pad 14 only in a single spot at the center of thesupporting surface of the pad 14, with, for example, a wood screw. Aseal 41 is provided between the barrier member 8 and the circumferenceof the screw head by means of welding or adhesive. This arrangement canapply also to the construction in which the barrier member is made ofthe thin synthetic resin plate 7. FIG. 9 shows the only spot in whichthe synthetic resin plate 7 is secured to the pad 14 by means of a woodscrew. A synthetic resin film 44, attached to the screw head 42 and tothe synthetic resin plate 7 by means of adhesive 43, provides a seal.

When the barrier member 8 is secured to the pad 14 only in a single spotat the center of the supporting surface of the pad 14, distortion of thebarrier member as a result of the swelling or sagging thereof can bechecked even though the barrier member is thin, and relative expandingand contracting movements will not be transmitted between the pad plate16 and the barrier member 8, since such movements are centered on theabove-mentioned spot at which the barrier member is secured to the pad.

As is apparent from the foregoing description of the preferredembodiments, the present invention overcomes the problems of thermalstress concentration at the barrier member joints fixed to the couplingjoists throughout the very great variation in temperature acting on thebarrier members from the charging and discharging of the tank withliquified gas. The thermal stress operating upon the barrier member issmall, and there is no possibility that the thermal stress caused by theexpansion and contraction of the pads acts upon the barrier members.Moreover, the barrier members are supported by the pads, and for thisreason do not distort. Consequently, the barrier members can be almostfree of harmful influences, while of plane, thin, simple and economicalconstruction.

We claim: 1. A low temperature liquified gas storage tank having a rigidouter wall, a low temperature resistant, liquid-tight inner wall spacedinwardly of the outer wall, and a heat insulating material between theouter and inner walls, wherein:

the inner wall comprises a plurality of rectangular barrier membersinterconnected to'form junctions between adjacent ones of said barriermembers;

coupling joists are attached to said outer wall and are arranged in arectangular checkerboard pattern with each rectangular area thereofcorresponding in size to a single barrier member;

rectangular box-like pressure pads are arranged so that each pressurepad is in one of the rectangular areas defined by said coupling joists,said pressure pads being spaced from said coupling joists and beingattached to the outer wall, each pressure pad consisting of a plateengageable by one of the barrier members and'capable of coveringsubstantially an-entire one of said rectangular areas, and legs securedto the plate;

said barrier members having their junctions located on the couplingjoists and attached thereto but not to the pressure pads; and

said insulating material is packed into the remaining void space betweenthe outer and inner walls.

2. A low temperature liquified gas storage tank according to claim 1wherein the barrier members are made of plywood having a layer of liquidtight material.

3. A low temperature liquified gas storage tank ac cording to claim 1wherein the barrier members are made of sheet metal.

4. A low temperature liquified gas storage tank according to claim 1wherein the barrier members are made of synthetic resin plates.

5. A low temperature liquified gas storage tank according to claim 1wherein the plate and legs of the pressure pad are made of plywood.

6. A low temperature liquified gas storage tank according to claim 1wherein at least some of the barrier 'members are secured to the plateof the pressure pad associated therewith in one spot located centrallyof such plate.

7. A liquified gas storage tank according to claim 1 wherein eachcoupling joist is T-shaped in section, the T-shaped section having a legportion which is attached to the outer wall of the tank.

8. A low temperature liquified gas storage tank according to claim 7wherein each coupling joist is made of plywood.

1. A low temperature liquified gas storage tank having a rigid outerwall, a low temperature resistant, liquid-tight inner wall spacedinwardly of the outer wall, and a heat insulating material between theouter and inner walls, wherein: the inner wall comprises a plurality ofrectangular barrier members interconnected to form junctions betweenadjacent ones of said barrier members; coupling joists are attached tosaid outer wall and are arranged in a rectangular checkerboard patternwith each rectangular area thereof corresponding in size to a singlebarrier member; rectangular box-like pressure pads are arranged so thateach pressure pad is in one of the rectangular areas defined by saidcoUpling joists, said pressure pads being spaced from said couplingjoists and being attached to the outer wall, each pressure padconsisting of a plate engageable by one of the barrier members andcapable of covering substantially an-entire one of said rectangularareas, and legs secured to the plate; said barrier members having theirjunctions located on the coupling joists and attached thereto but not tothe pressure pads; and said insulating material is packed into theremaining void space between the outer and inner walls.
 2. A lowtemperature liquified gas storage tank according to claim 1 wherein thebarrier members are made of plywood having a layer of liquid tightmaterial.
 3. A low temperature liquified gas storage tank according toclaim 1 wherein the barrier members are made of sheet metal.
 4. A lowtemperature liquified gas storage tank according to claim 1 wherein thebarrier members are made of synthetic resin plates.
 5. A low temperatureliquified gas storage tank according to claim 1 wherein the plate andlegs of the pressure pad are made of plywood.
 6. A low temperatureliquified gas storage tank according to claim 1 wherein at least some ofthe barrier members are secured to the plate of the pressure padassociated therewith in one spot located centrally of such plate.
 7. Aliquified gas storage tank according to claim 1 wherein each couplingjoist is T-shaped in section, the T-shaped section having a leg portionwhich is attached to the outer wall of the tank.
 8. A low temperatureliquified gas storage tank according to claim 7 wherein each couplingjoist is made of plywood.